Examination of the kinetics and mechanisms of key reactions of hemerythrin, the oxygen-carrying protein derived from the sipunculan worm Golfingia gouldii will be continued. Oxidation of deoxy- and oxy-hemerythrin by Fe(III) cyano complexes, and reduction of methemerythrin by dithionite ion and other reducing agents (including metalloproteins) will be examined. Our previous observations of anion interactions with deoxyhemerythrin, will lead us to examine substitution reactions with other potential ligands. Conventional and stopped flow spectrophometry will be used to assess the interactions quantiatively and to examine their kinetics. It is hoped that the results, taken in conjunction with the known behavior of simple iron complexes, will allow an assessment of the importance of the protein on the properties of the two metal centers in this efficient oxygen carrier. Comparisons will be sought with other respiratory proteins.